Powertrain, generic · Ignition system or misfire

P03FD Ignition L Control Signal Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Ignition L is one of up to twelve control signal lines (A to L) from the engine module to an ignition coil with integrated output stage or to an ignition module – plausibly the 12th channel, but the code standard leaves the assignment to the manufacturer. The code concerns this logic-level signal, not the coil's primary circuit (coil L has its own codes, P0362 and P2333 ff). P03FD means the control line is open or high-resistance: with its driver switched off the module sees a voltage that indicates a missing load (GM uses more than 30 kΩ for comparable coil drivers). The coil fires wrongly or not at all; the misfire usually also sets P0300 ff, and many modules shut off injection to that cylinder to protect the catalyst. No manufacturer document available to us uses this code – it would only concern twelve-cylinder engines, whose makers publish no OBD summaries; GM and Ford tables stop at eight and ten cylinders.

Likely causes

Control line or connector pin open (corrosion, pushed-back pin)
Coil with integrated output stage or ignition module faulty
Supply or ground of the coil or module missing
Driver in the engine module

Symptoms

  • Check engine light on, may flash with severe misfire
  • Misfire on the cylinder of this channel, rough running
  • Loss of power, cylinder possibly shut off

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ignition control lignition coil driverignition wiringengine control module

Related codes

P03FEP03FFP0362P0312P0300

References: law.cornell.edu, patents.google.com, gsi.ext.gm.com.